The network elements of telecommunications networks such as SDH networks require management information for data transfer. In order to be able to provide such information to the individual network elements from a central point, nowadays the network elements are usually interconnected via a data channel network (DCN) for the transmission of management data. Management of the traffic is via PCs or UNIX computers which provide the management data to one of the network elements via a management interface.
For example the standardised Q3 protocol can be used for managing network elements, with the management data being transported between the individual network elements in areas of the header of data blocks, reserved for the data channel network, such as within the header areas of a multiplexer or a regeneration section of SDH signals.
Frequently however, network elements used provide for non-standardised protocols for management. This can lead to problems in areas where network elements from various providers are used if for the transmission of management data from one network element which for example provides for the use of the Q3 protocol, a path to the other such network element is used which leads via network elements with another management protocol. This means that the areas of the header of data blocks which according to the Q3 protocol are provided for management data, cannot be used for transporting management data because these areas may be used for other purposes by the network elements using another management protocol. Thus in this case transmission of management data by means of standardised Q3 routing and thus remote managing of the target network element is not possible. The same problem occurs analogously with any other management protocol which is based on the transmission of management data in the header area of data signals.
For illustration, FIG. 2 shows an example of a section of a telecommunications network with network elements from various providers. The network is divided into a first area A with network elements NEA1–NEA3 of the provider A and a second area B with network elements NEB1–NEB3 of provider B. The connections between the shown network elements NEA1–NEA3 of provider A are all routed via network elements NEB1–NEB3 of provider B. All data which is to be transmitted from one of the network elements NEA1–NEA3 to another of the network elements NEA1–NEA3, thus needs to be forwarded from network elements NEB1, NEB2, NEB3 of provider B.
The network element NEA1 of provider A comprises a Q3 management interface by way of which management data can be input by a remote computer. In the example shown, this management data which is inserted in the areas of the header provided for this purpose, of the data blocks leaving the network element, cannot simply be transmitted to the network elements NEA2, NEA3 which also need this management data, because the Q3 areas in the header of the data blocks in the area with network elements NEB1, NEB2, NeB3 of provider B may be used for different purposes.
The same problem is encountered if different network elements provide for routing of management data according to a single management protocol, but the network operator desires strict separation between management of various groups of network elements.
Similarly, equipment of various manufacturers may be used layer by layer, with separate management being necessary.
For this reason, in practice, so-called “tunnelling” is used for the transmission of management data via network elements which provide for another management protocol or for separate management.
With tunnelling, data which usually, in accordance with a particular management protocol, is transported to areas in the header of data blocks provided for this purpose, is inserted into the area of the payload. During subsequent transmission of data it is then immaterial what software protocols in network elements of other providers by way of which transmission takes place, are used. The data in the area of the payload is not subject to interpretation and distribution by software. Instead, simple byte-by-byte transmission is carried out, with strict standardisation existing in planes in close physical proximity, which standardisation is applied equally by all providers.
Insertion of management data which is really transported in the header of the data blocks, into the area for the payload, takes place via termination points TP in a network element (head-end NE) which has access to management data according to protocol. Here, the term “access according to protocol” designates access which is provided according to the management protocol used by the network elements between which management data is to be transmitted. Such access according to protocol can for example exist in a management interface integrated into the network element, with the management data being input by an associated computer. But access can also consist of receiving data blocks with the management data in the header area provided for this purpose, by another network element which uses the same management protocol.
The network element with access according to protocol, to the management data, comprises a termination point TP for every other network element which needs to be supplied with management data via tunnelling. Starting from the network element to which the management data is directly made available, in a star-shaped manner, tunnels are formed to the other network elements in which the management data is transmitted in the area of the payload of data blocks. Each of the destination network elements comprises a termination point TP by means of which the management data is taken from the payload area and inserted into the header of a data block.
In the case of SDH networks, for transmission in the payload area, management data can for example be inserted into suitable areas of the transported virtual containers (VCs) within the STM signal or the PDH signal. Possible suitable insertion points may be one or several bits in the R-bytes (reserved but so far unused) of VC-12 containers. Further possibilities may be one or several bits in the standard F2 byte or in one of the time slots, in particular time slot 0, of a transported 2M signal.
If a large number of network elements are to be centrally managed by tunnelling, via a single management access in one of the network elements, the problem is encountered that the network element with access according to protocol, to the management data, needs to comprise a large number of termination points, namely one TP for each of the other network elements to be managed, which are reached via network elements working with another management protocol. Thus this necessitates considerable effort by this particular network element. Furthermore, there is the possibility that in extraneous networks comprising network elements with other management protocols, unnecessary capacity is used if the same data is to be transported several times over longer distances. In addition it must also be borne in mind that in the case of a failure of a tunnel, the associated network element is for the time being cut off from the supply of management data.